Recently, the IEEE802.16WG (Working Group) has pursued the standardization and the development of a system called WiMAX, as an intermediate-distance large-amount wireless communications system, which WiMAX system employs the OFDMA (Orthogonal Frequency Domain Multiple Access) scheme that realizes flexible multiplexing to a wireless frame in the frequency axis direction and the time axis direction. In this instance, the IEEE802.16WG mainly regulates two types: IEEE802.16d (for example, see IEEE 802.16d-2004) intended for fixed communications use and particular, the latter technology can be called “mobile WIMAX”).
These IEEE802.16d and IEEE802.16e (hereafter, these will be simply called “WIMAX standard” without distinguishing therebetween) regulate that a wireless terminal (MS: Mobile Station) performs communications between a BS (BS: Base Station) and the MS in obedience to MAP information contained in a wireless frame sent by the wireless base station.
That is, basically, the MS performs reception processing to a field called a burst which is specified with MAP information (DL-MAP) in a downlink (DL) sub-frame in a wireless frame expressed with the two dimensional region in the time axis (symbol time) direction and the frequency (frequency channel) direction, and also performs transmission processing by use of the burst specified with the UL-MAP, which is uplink MAP information. That is, the MAP information is regarded as information (burst allocation information) which specifies (allocates) the regions (reception region and transmission region) to be received and sent by the MS.
Here, as indicated in FIG. 8, in the wireless frame, both of (1) a control-system message and (2) user data are transmitted after addition of a MAC (Media Access Control) header thereto and conversion into a packet performed. That is, a GMH (Generic MAC Header) under the WiMAX standard having such a header format as is indicated in FIG. 9, is added to both of the control-system message and the user data. In this instance, in the following description, the term of “packet” means a MAC-SDU (Service Data Unit) (hereinafter, will be simply called “SDU”) such as an IP (Internet Protocol) packet and an ATM (Asynchronous Transfer Mode) cell, and the MAC-SDU (payload area) with header information, such as a GMH and a sub-header, added thereto is called MAC-PDU (Protocol Data Unit) (or simply “PDU”). The PDU is a data unit coped with by the protocol of the packet.
Thus, no distinguishing is made between a control-system message (also called “MAC management data”) and user data on the air, but in the BS or the MS, these are distinguished therebetween based on a connection identifier (CID) [a total of 16 bits (MSB 8 bits and LSB 8 bits, indicated by the diagonally shaded areas in FIG. 9)] set as the information element of the GMH.
That is, the CID is defined in advance as a CID indicating that it is a control-system message and a CID indicating that it is user data. For example, as a control-system message, three types of CID values (fixed values each added to each MS): the Basic CID; the Primary CID; and the Initial Ranging CID. As the CID of user data, a CID value called “Transport CID” is defined.
Therefore, the MS and the BS detects and analyzes the above mentioned GMH added to transceived data to confirm the CID, thereby making it possible to recognize whether the data is a control-system message or user data (that is, distinguish between a control channel and a data channel). In this instance, the type of the control-system message itself is identified by the type information (TYPE value) set to the management message type field [see FIG. 8(1)] of the payload area.